Acute theophylline toxicity is still an important cause of intoxication with major consequences; significant morbidity and mortality. Conflicting reports about both age and serum theophylline concentrations as predictors for development of major toxic effects were suggested by many authors. However, little is known about electrocardiography (ECG) as predictor of mortality and major outcome events in acute theophylline poisoned patients. The current observational cross sectional study was conducted to evaluate electrocardiographic findings as predictor of mortality and major outcome events [intensive care unit (ICU) admission, need for mechanical ventilation and need for hemodialysis] in acute theophylline toxicity. Twenty eight adult patients acutely exposed to theophylline have participated in the study. The severity of symptoms and signs of acute theophylline poisoning was graded into mild, moderate and severe grade theophylline poisoning. Electrocardiography was recorded and analyzed for rate, rhythm, axis, voltage, ST and T wave abnormalities, conduction defects, PR interval. The ECG changes induced by acute theophylline poisoning were graded into minor, moderate and severe. Corrected QT interval (QTc) was estimated according to Bazett's formula; QTc= QT/ √RR. Both normal and severe ECG changes were recorded in seven (25%) patients each. Meanwhile, moderate ECG changes were verified in 14 (50%) of patients. Fourteen patients (50 %) showed a prolonged QTc interval. Grading of ECG changes revealed significant statistical association with theophylline poisoning severity, theophylline level and major outcome events (ICU admission and need for hemodialysis). Meanwhile, no significant statistical association was perceived between QTc interval and any of sociodemographic, toxicological & clinical data, mortality and major outcome events.